pdfio/CONTRIBUTING.md

Contributing to PDFio

PDFio is developed and distributed as open source software under the Apache License, Version 2.0. Contributions should be submitted as pull requests on the Github site:

http://github.com/michaelrsweet/pdfio/pulls

Contents

• Build System
• Version Numbering
• Coding Guidelines
  • Source Files
  • Header Files
  • Comments
  • Indentation
  • Spacing
  • Return Values
  • Functions
  • Variables
  • Types
  • Structures
  • Constants
• Shell Script Guidelines
• Makefile Guidelines
  • General Organization
  • Makefile Documentation
  • Portable Makefile Construction
  • Standard Variables
  • Standard Targets
  • Object Files
  • Programs
  • Static Libraries
  • Shared Libraries
  • Dependencies
  • Install/Uninstall Support

Build System

The build system uses GNU autoconf to create a simple POSIX makefile to build static and/or shared libraries. To improve portability, makefiles must not make use of features unique to GNU make. See the Makefile Guidelines section for a description of the allowed make features and makefile guidelines.

An Xcode project is provided for macOS/iOS developers, and a Visual Studio solution and projects for Windows developers.

Version Numbering

PDFio uses a three-part version number separated by periods to represent the major, minor, and patch release numbers. Major release numbers indicate large design changes or backwards-incompatible changes to the library. Minor release numbers indicate new features and other smaller changes which are backwards- compatible with previous releases. Patch numbers indicate bug fixes to the previous feature or patch release.

Production releases use the plain version numbers:

MAJOR.MINOR.PATCH
1.0.0
1.0.1
1.0.2
...
1.1.0
...
2.0.0

The first production release in a MAJOR.MINOR series (MAJOR.MINOR.0) is called a feature release. Feature releases are the only releases that may contain new features. Subsequent production releases in a MAJOR.MINOR series may only contain bug fixes.

Beta-test releases are identified by appending the letter B to the major and minor version numbers followed by the beta release number:

MAJOR.MINORbNUMBER
1.0b1

Release candidates are identified by appending the letters RC to the major and minor version numbers followed by the release candidate number:

MAJOR.MINORrcNUMBER
1.0rc1

Note: While the beta/release candidate syntax is not strictly compatible with Semantic Versioning, it is better supported by the various traditional package formats. When packaging a pre-release version of PDFio in a format that requires the use of semantic version numbers, the version number should simply be converted to the form "MAJOR.MINOR.0-suffix".

Coding Guidelines

Contributed source code must follow the guidelines below. While the examples are for C source files, source code for other languages should conform to the same guidelines as allowed by the language.

Source Files

All source files names must be 16 characters or less in length to ensure compatibility with older UNIX filesystems. Source files containing functions have an extension of ".c" for C source files. All "include" files have an extension of ".h". Tabs are set to 8 characters or columns.

The top of each source file contains a header giving the purpose or nature of the source file and the copyright and licensing notice:

//
// Description of file contents.
//
// Copyright © YYYY by AUTHOR.
//
// Licensed under Apache License v2.0.  See the file "LICENSE" for more
// information.
//

Header Files

Private API header files must be named with the suffix "-private", for example the "pdfio.h" header file defines all of the public APIs while the "pdfio-private.h" header file defines all of the private APIs. Typically a private API header file will include the corresponding public API header file.

Comments

All source code utilizes block comments within functions to describe the operations being performed by a group of statements; avoid putting a comment per line unless absolutely necessary, and then consider refactoring the code so that it is not necessary. C source files use the C99 comment format ("// comment"):

// Clear the state array before we begin...
for (i = 0; i < (sizeof(array) / sizeof(sizeof(array[0])); i ++)
  array[i] = PDFIO_STATE_IDLE;

// Wait for state changes on another thread...
do
{
  for (i = 0; i < (sizeof(array) / sizeof(sizeof(array[0])); i ++)
    if (array[i] != PDFIO_STATE_IDLE)
      break;

  if (i == (sizeof(array) / sizeof(array[0])))
    sleep(1);
} while (i == (sizeof(array) / sizeof(array[0])));

Indentation

All code blocks enclosed by brackets begin with the opening brace on a new line. The code then follows starting on a new line after the brace and is indented 2 spaces. The closing brace is then placed on a new line following the code at the original indentation:

{
  int i; // Looping var

  // Process foobar values from 0 to 999...
  for (i = 0; i < 1000; i ++)
  {
    do_this(i);
    do_that(i);
  }
}

Single-line statements following "do", "else", "for", "if", and "while" are indented 2 spaces as well. Blocks of code in a "switch" block are indented 4 spaces after each "case" and "default" case:

switch (array[i])
{
  case PDFIO_STATE_IDLE :
      do_this(i);
      do_that(i);
      break;

  default :
      do_nothing(i);
      break;
}

Spacing

A space follows each reserved word such as if, while, etc. Spaces are not inserted between a function name and the arguments in parenthesis.

Return Values

Parenthesis surround values returned from a function:

return (PDFIO_STATE_IDLE);

Functions

Functions with a global scope have a lowercase prefix followed by capitalized words, e.g., pdfioDoThis, pdfioDoThat, pdfioDoSomethingElse, etc. Private global functions begin with a leading underscore, e.g., _pdfioDoThis, _pdfioDoThat, etc.

Functions with a local scope are declared static with lowercase names and underscores between words, e.g., do_this, do_that, do_something_else, etc.

Function names follow the following pattern:

• "pdfioFooCreate" to create a Foo object,
• "pdfioFooDelete" to destroy (free) a Foo object,
• "pdfioFooGetBar" to get data element Bar from object Foo,
• "pdfioFooIsBar" to test condition Bar for object Foo, and
• "pdfioFooSetBar" to set data element Bar in object Foo.
• "pdfioFooVerb" to take an action with object Foo.

Each function begins with a comment header describing what the function does, the possible input limits (if any), the possible output values (if any), and any special information needed:

//
// 'pdfioDoThis()' - Short description of function.
//
// Longer documentation for function with examples using a subset of
// markdown.  This is a bulleted list:
//
// - One fish
// - Two fish
// - Red fish
// - Blue fish
//
// > *Note:* Special notes for developer should be markdown block quotes.
//

float                  // O - Inverse power value, 0.0 <= y <= 1.1
pdfioDoThis(float x)   // I - Power value (0.0 <= x <= 1.1)
{
  ...
  return (y);
}

Return/output values are indicated using an "O" prefix, input values are indicated using the "I" prefix, and values that are both input and output use the "IO" prefix for the corresponding in-line comment.

The codedoc documentation generator also understands the following special text in the function description comment:

@deprecated@         - Marks the function as deprecated (not recommended
                       for new development and scheduled for removal)
@since version@      - Marks the function as new in the specified version.
@private@            - Marks the function as private (same as starting the
                       function name with an underscore)

Variables

Variables with a global scope are capitalized, e.g., ThisVariable, ThatVariable, ThisStateVariable, etc. Globals must not be used in the PDFio library.

Variables with a local scope are lowercase with underscores between words, e.g., this_variable, that_variable, etc. Any "local global" variables shared by functions within a source file are declared static.

Each variable is declared on a separate line and is immediately followed by a comment block describing the variable:

int         ThisVariable;    // The current state of this
static int  that_variable;   // The current state of that

Types

All type names are lowercase with underscores between words and _t appended to the end of the name, e.g., pdfio_this_type_t, pdfio_that_type_t, etc. Type names start with the "pdfio_" prefix to avoid conflicts with system types. Private type names start with an underscore, e.g., _pdfio_this_t, _pdfio_that_t, etc.

Each type has a comment block immediately after the typedef:

typedef int pdfio_this_type_t;  // This type is for foobar options.

Structures

All structure names are lowercase with underscores between words and _s appended to the end of the name, e.g., pdfio_this_s, pdfio_that_s, etc. Structure names start with the "pdfio_" prefix to avoid conflicts with system types. Private structure names start with an underscore, e.g., _pdfio_this_s, _pdfio_that_s, etc.

Each structure has a comment block immediately after the struct and each member is documented similar to the variable naming policy above:

struct pdfio_this_struct_s // This structure is for foobar options.
{
  int this_member;         // Current state for this
  int that_member;         // Current state for that
};

One common design pattern is to define a private structure with a public typedef, for example:

// In public header
typedef struct _pdfio_foo_s pdfio_foo_t // Foo object

// In private header
struct _pdfio_foo_s        // Foo object
{
  int this_member;         // Current state for this
  int that_member;         // Current state for that
};

Constants

All constant names are uppercase with underscores between words, e.g., PDFIO_THIS_CONSTANT, PDFIO_THAT_CONSTANT, etc. Constants begin with the "PDFIO_" prefix to avoid conflicts with system constants. Private constants start with an underscore, e.g., _PDFIO_THIS_CONSTANT, _PDFIO_THAT_CONSTANT, etc.

Typed enumerations should be used whenever possible to allow for type checking by the compiler. The constants for typed enumerations must match the type name in uppercase, for example a pdfio_foo_e enumeration has constant names starting with PDFIO_FOO_.

Comment blocks immediately follow each constant:

typedef enum pdfio_style_e  // Style enumerations
{
  PDFIO_STYLE_THIS,         // This style
  PDFIO_STYLE_THAT          // That style
} pdfio_style_t;

Shell Script Guidelines

All shell scripts in PDFio must conform to the POSIX shell command language and should restrict their dependence on non-POSIX utility commands.

Makefile Guidelines

PDFio uses a single POSIX makefile to build it. GNU make extensions MUST NOT be used.

The following variables are defined in the makefile:

• AR; the static library archiver command,
• ARFLAGS; options for the static library archiver,
• CC; the C compiler command,
• CFLAGS; options for the C compiler,
• CODESIGN_IDENTITY: the code signing identity,
• CPPFLAGS; options for the C preprocessor,
• DESTDIR/DSTROOT: the destination root directory when installing.
• DSO; the shared library building command,
• DSOFLAGS; options for the shared library building command,
• LDFLAGS; options for the linker,
• LIBPDFIO: the name of the primary (shared or static) library
• LIBPDFIO_STATIC: the name of the secondary (static) library
• LIBS; libraries for all programs,
• OPTIM; common compiler optimization options,
• prefix; the installation prefix directory,
• RANLIB; the static library indexing command,
• SHELL; the sh (POSIX shell) command,
• VERSION: the library version number.

The following standard targets are defined in the makefile:

• all; creates the static library and unit test program.
• clean; removes all target programs libraries, documentation files, and object files,
• install; installs all distribution files in their corresponding locations.
• test; runs the unit test program, building it as needed.